It is well recognized that proper and uniform spacing of seed in the furrow is essential to maximizing crop yield. The first step in achieving uniform spacing is to accurately dispense one seed and one seed only at the proper timing. This “singulation” accuracy is a performance benchmark that is well known for many types of seed meters and is often tested on a seed meter test stand prior to the beginning of the planting season. The second step is to deliver the seed to the furrow with the same (or nearly the same) consistency of spacing as the seeds are discharged by the meter. The vast majority of agricultural planters rely upon a seed tube to direct the seeds downwardly and rearwardly from the meter and into the furrow.
There are many different types of seed meters, but each of the different types will fall into one the general classes of meters: (i) mechanical seed meters, such as disclosed in U.S. Pat. No. 3,627,050 to Hansen et al.; (ii) air seed meters, such as disclosed in U.S. Pat. No. 3,888,387 to Deckler; and (iii) vacuum seed meters, such as disclosed in U.S. Pat. No. 5,170,909 to Lundie et al. Many of these meters have historically operated at singulation accuracies of between 90 to 95%. Recent improvements to mechanical meters have resulted in singulation accuracies as high as 98 to 99%. The vacuum meter, too, has achieved singulation accuracy of up to 99% on some seed types but vacuum meters are often plagued with several problems.
One of the problems plaguing singulation accuracy of vacuum meters in general is the recently developed seed coatings often applied to the seed for treatment of rootworm and secondary pests. These seed coatings make it more difficult to entrain the seed over the apertures in the vacuum disks. Another problem affecting singulation accuracy with vacuum meters that utilize “celled-disks” (i.e., disks with indentations or “cells” around each aperture in the disk, such as the disks disclosed in U.S. Pat. No. 5,170,909 to Lundie et al.), is that such meters have a higher tendency to plant “skips” and “doubles” in near succession when planting flat shaped seeds. Despite this tendency, however, celled-disk vacuum meters offer the unique advantage of permitting the meter to generally operate at lower vacuum levels than meters that use flat or non-celled disks (i.e., vacuum disks with apertures only) because the indentations or cells assist in holding the seeds in place, thus requiring less vacuum pressure to entrain the seeds.
In order to reduce the higher amount of skips and doubles generally experienced when using celled-disk vacuum meters, most celled-disk vacuum meters, such as the John Deere MaxEmerge® vacuum meter, utilize different celled-disks each with a different cell profile and/or aperture configuration. These celled-disks must be changed or swapped-out based upon the size of the seed being planted to achieve acceptable singulation accuracies. For example, the MaxEmerge vacuum meter has different celled-disks for field corn, popcorn, sweet corn, soybeans, cotton, sorghum, sugar beets, sunflowers, edible beans/peas, peanuts, and for melons/squash/cucumbers.
Another problem with celled vacuum disks is that spacing accuracy is adversely affected because the seed must slide out of the cell, subjecting sequential seeds to random and variable release times due to differences friction, seed orientation, etc. The end result is that with celled-disk vacuum meters, singulation accuracy is often poor with many flat seed types and seed spacing is inconsistent spacing on nearly all seed types.
In an attempt to improve singulation accuracy, farmers have tried to use non-celled disks with meters originally designed for celled-disk meters. For example, with the John Deere MaxEmerge vacuum meters, farmers started using one of the specialty disks designed by John Deere for planting irregular seeds such as sweet corn (thus, this disk is often referred to as the “sweet corn disk”). The sweet corn disk is flat on the planting surface and does not have any indentations or cells to hold the seed. Therefore, the timing of release of the seeds from the disk is more consistent because the aforementioned seed release problem due to friction, etc. is eliminated thereby reducing the amount of skips.
Similar to the sweet corn disk, an update kit, known as the Accu-Vac Update Kit, available from S.I. Distributing, Inc. St. Marys, Ohio, utilizes a flat, non-celled disk. The Accu-Vac disk has larger apertures in order to ensure the seeds are adequately entrained so they do not prematurely slough-off as the disk rotates. Unfortunately, by increasing the aperture size, the vacuum flow must necessarily increase in order to maintain the same amount of negative pressure to prevent the seeds from prematurely sloughing-off. Some planter vacuum systems are not capable of supplying the vacuum flow necessary to utilize the Accu-Vac update kit.
While the sweet corn disk and the Accu-Vac disk have markedly increased singulation performance when used in place of celled-disk, their use has also resulting in a significant decrease in the accuracy and uniformity of in-furrow seed-to-seed spacing. This is due to the fact that the trajectory of the seed upon release from these flat disks is not the same as the trajectory of the seed when released from a celled-disk for which the meter was originally designed. It should be appreciated that with celled-disks, the indentation of the cell imparts a horizontal velocity to the seed as it slides out from the cell. Vacuum meters originally designed for use with celled-disks, such as the MaxEmerge vacuum meter, have the centerline of the seed tube offset a predetermined horizontal distance to account for the horizontal distance traveled by the seed upon its entry into the seed tube. Thus, because flat non-celled disks do not impart a horizontal velocity to the seed upon release, the seed will not enter the seed tube at its centerline. As a result, the seeds will tend to experience more ricochet as they travel down the seed tube as opposed to free-falling and then smoothly sliding along the forward wall of the seed tube as would otherwise generally be experienced if the seed entered the seed tube at its centerline if released from a celled-disk. Tests have shown that the more seeds ricochet within the seed tube, the more inconsistent will be the in-furrow seed-to-seed spacing. This is due to sequential seeds traveling at different velocities through the tube. For example, if one seeds ricochets off the sidewalls of the seed tube three times before being dispensed into the furrow versus a seed that does not ricochet at all, or a seed that only ricochets once or twice, the seeds experiencing more ricochet will exit the seed tube at a slower velocity than those experiencing fewer ricochets. This difference in seed velocity upon exiting the seed tube results in inconsistent seed-to-seed spacing in the furrow.
Accordingly, there remains a need for an improved vacuum seed meter and/or a retro-fit kit for use with existing vacuum seed meters such as the John Deere MaxEmerge vacuum meter that can deliver very high seed singulation accuracy as well as in-furrow seed to seed spacing while requiring minimal swapping-out of disks and minimal adjustment to the singulators or other components of the meter.